from typing import *


class Solution:
    def findOriginalArray(self, changed: List[int]) -> List[int]:
        changed.sort()
        q = []
        ans = []
        for v in changed:
            if len(q) > 0 and v == q[0] * 2:
                ans.append(q.pop(0))
            else:
                q.append(v)
        return ans if len(q) == 0 else []


s = Solution()
print(s.findOriginalArray([1, 3, 4, 2, 6, 8]))
